Re: [RFC] frandom - fast random generator module

[Ingo Oeser]

On Thursday 16 October 2003 10:22, Eli Billauer wrote:
> (3) I agree with both. And I use /dev/zero a lot. I know how to write a
> zero-generating application in user space.

There is a good reason for this: You can implement pages containing only
zeroes very efficiently in the kernel. You can map pages containing only
zeroes to a single physical page in the kernel (the ZERO_PAGE). You can
ignore the refcounting on this page and save precious cache flushes and
much more by doing this in the kernel.

Compare an application with memset() and mmaping of /dev/zero in
multiple processes, writing to only some of these pages later.

> (4) The module is small: 6kB of source code as a standalone module, and
> 2.3 kB of kernel memory.

That's a price worth as an "default to off" option. We have much more
seldom used stuff in the kernel and maintain it, which is a bigger mess
than this.


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